When we get tattooed, the ink is deposited as a pigment in the dermis of our skin, explains dermatologist Dr. Lauren Ploch. This is below the top layer of skin–the epidermis–but above the skin’s fat. Cells in the dermis are replaced much more slowly than in the epidermis, which is why tattoos don’t fade as we shed skin cells. Your first consideration before getting a tattoo should be needle hygiene. Unclean needles spread infection and disease.
When tattoo ink enters your skin, your body recognizes it as foreign, says dermatologist Dr. Lauren Moy. That causes the body to recruit immune cells to the area. This is why newly tattooed skin can become inflamed or sensitive. In most cases, careful after-tattoo care can mitigate most of these reactions. This includes keeping the tattooed skin area clean, using moisturizer, and avoiding exposure to sun or water.
The immune cells that flood into your newly tattooed skin include macrophages–specialists in munching foreign molecules. These cells devour the pigment but struggle to break it down. This means the ink in our tattoos is distributed between skin and immune cells. When macrophages die, they release their contents, but that ink is rapidly eaten by other macrophages in the area. This “capture” and “recapture” process holds ink in place in the skin.
A 2018 case study reported the case of a heavily tattooed cancer patient whose mastectomy went in an unexpected direction when her surgeons noted her lymph nodes had turned black. An incorrect diagnosis could have led to the woman being treated for malignant melanoma. Luckily, her doctors realized the color was caused by broken-down tattoo ink building up in the nodes. Their analysis showed the discoloration wasn’t dangerous.